I think tiger barbs would work fine as well. The reason I suggest the dithers is that I think when small, the cichlids may feel a bit out in the open and will hide most of the time. The dithers help them feel more secure. If you don't want them, don't put them in. If your fish are already adult size, this wouldn't be as big an issue. It's your tank, so do what you like.
The JD shouldn't bother the pleco as long as they are similar sizes to start with. If you throw a 1" pleco in with an 8" JD, the pleco will be a snack.